This longitudinal study is based upon the hypothesis that children with AD/HD represent a neurologically vulnerable group, but that the quality of parenting characteristics affects the manifestation and severity of symptoms. As such, evidence of neurological vulnerability, as assessed by neuropsychological tests in preschool children may be particularly useful for distinguishing between those "at risk" children who do and do not go on to develop AD/HD. Further, by assessing the quality of parenting skills during the preschool age, we hypothesize that there will be an interaction such that the combination of neuropsychological deficits and negative parenting characteristics will portend adverse outcome during the school-age years for at risk preschool children. The primary aim is to determine whether neuropsychological and parenting factors, independently and in combination, distinguish between inattentive/hyperactive preschool children who do and do not develop AD/HD. The goal is to recruit and follow a large sample of 3 and 4 year-old "at risk" and control children for whom behavioral, neuropsychological and parenting data are collected at baseline. Subsequently, behavioral ratings will be gathered every six months, and more in-depth clinical, neuropsychological and parenting assessments will be conducted annually. The primary dependent measures for this study will be collected when the children are six years-old. In addition, a secondary aim is to examine the extent to which genetic status has predictive validity for the emergence of ADHD, and the degree to which genetic status relates to neuropsychological findings and interacts with parenting factors in the emergence of AD/HD.